Nokia's Lumia 900 was supposed to reboot the Finnish company's fortunes and provide a showcase for Microsoft's Windows Phone 7 operating system. Just three months after its launch, though, the most-hyped Windows Phone is starting to look obsolete. Rob Pegoraro revisits the phone he tested in April.

Instead, the 900 -- originally priced at $100 but recently slashed to $50, and available exclusively on AT&T's network in the United States -- won't advance past a "Windows Phone 7.5 refresh" patch and a later WP 7.8 update adding WP8's more customizable start screen.

But the current software itself doesn't feel old, aside from its embarrassing reliance on desktop programs to sync files and install even minor updates. This operating system's basic innovation -- making the start screen a stack of easily rearranged, interactive tiles that present notifications from your apps -- remains an intelligent, fast way to stay on top of your life.

The hope that the Lumia would reboot the entire Windows Phone market hasn't panned out, though. WP7's 1.3% share of the smartphone installed base remains smaller than that of the unlovable Windows Mobile software it replaced, according to Nielsen's figures.

There are small signs of progress: From the first quarter of 2012 to May, NPD Group data shows WP7's share of each month's smartphone sales doubling from 2% to 4%. "The Lumia 900 far and away has been driving the increase," said analyst Ross Rubin.